Various inorganic and organic compounds have been known as photographically useful reagents. Organic photographically useful reagents include water-soluble, water-insoluble or sparingly water-soluble compounds. Among these water-insoluble and sparingly water-soluble compounds, oil-soluble photographically useful reagents such as dye image-forming couplers, dye providing redox compounds, ultra violet absorbing agents, antifading agents, color mixing preventing agents and their precursors have gained particularly widespread acceptance. These compounds are introduced into hydrophilic colloid layers, usually in a finely dispersed form.
Many techniques have so far been developed in regard to the emulsification and dispersion of such oil-soluble photographically useful reagents. For example, U.S. Pat. Nos. 2,739,888 and 3,352,681 describe techniques in regard to ultra violet absorbing agents. U.S. Pat. Nos. 2,360,290, 2,728,659 and 3,700,453 describe techniques regarding diffusion-resistant alkylhydroquinones used to prevent color fogging, color staining, color mixing, etc. In particular, methods are known which effect emulsification and dispersion of oil-soluble photographic additives by using monomeric anionic surface-active agents as emulsifying agents. For example, U.S. Pat. No. 2,332,027 describes a method involving the use of Gardinol WA (a trade name for sulfonated coconut fatty alcohol, a product of E. I. du Pont de Nemours & Co.) and triisopropylnaphthalenesulfonic acid salts; Japanese Pat. No. 428,191 describes a method involving the use of, as an emulsifying agent, a water-soluble coupler having both a sulfone or carboxyl group and a long-chain aliphatic group; and U.S. Pat. No. 3,676,141 describes a method involving the use of a combination of an anionic surface-active agent having a sulfo group and a nonionic surface-active agent of the anhydrohexyl ester type. These emulsifying and dispersing methods, however, give coarse dispersed particles and cannot form fine particles of less than about 0.3 .mu.m in size required in the recent technology of photographic light-sensitive materials. Particularly, in the designing of a color photographic light-sensitive material, photographic elements (i.e., photographic layers) coated on a support are thick. If emulsion particles to be added thereto are coarse, light scattering which adversely affects the photographic properties of the light-sensitive material occurs during passage of the light through the photographic elements. This makes the photographic light-sensitive material opaque, and may cause a deterioration in the quality of images in regard to image sharpness, granularity, etc.
The surface-active polymer disclosed in Japanese Patent Application (OPI) No. 138726/78 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") gives a fine dispersion having excellent stability and can lead to the production of a photographic light-sensitive material in which or on the surface of which crystals of the aforesaid organic photographically useful reagents hardly precipitate. However, photographic light-sensitive materials obtained by using a dispersion of photographically useful reagents in water or a hydrophilic colloid composition together with such a surface-active polymer cause "contamination of processing solutions" as will be described hereinbelow, and consequently are reduced in merchandize value. The "contamination of processing solutions", as used herein, means the formation of a tarry substance called "scum" on the surface of a developing solution or on a wall surface.
If the hydrophilicity of the surface-active polymer is reduced by decreasing the proportion of the sulfonic acid group units or increasing the hydrophobic groups in order to prevent the surface-active polymer from being dissolved in the processing solution, the contamination of the processing solution is reduced, but the dispersed particles become coarse and drastically reduces the quality of the resulting image. If, conversely, the hydrophilicity of the polymer is increased by increasing the proportion of the sulfonic acid group units or decreasing the hydrophobic groups, the contamination of the processing solution cannot be reduced, and the dispersed particles become coarse.
For this reason, even when the structure of the surface-active polymer is varied within the range described in Japanese Patent Application (OPI) No. 138726/78, it is impossible to reduce the contamination of processing solutions and simultaneously provide finely dispersed particles.